Click on the guest's name, a new window opens. Click on the 'History' tab and you will see all the operations that have been done on this guest, all events combined.
In the 'Subject' column, you can see which elements have been modified and if an import has been made.
In the column 'New Data/Info', you can see the modified data.
In the 'Logged user' column, you can see who has made that modification:
An administrator of the platform via an import or a manual addition: 'name of the administrator'.
The participant via his registration form: 'Guest'.
In the 'Date' column, you will find the date and time when the change was made.